We already know that the solar wind gradually erodes the atmospheres of every planet in our solar system - even Earth, hidden under its protective magnetic field, isn't safe from the assault.
But of the rocky inner planets in our solar system, Earth was the lucky one. Many planetary scientists believe that Mars, Earth, and Venus began life as very similar worlds. Certainly, they condensed from the same cloud of dusty, planet forming material, so they must have originally had similar compositions. Needless to say, they didn't all turn out the same way.
PHOTOS: 5 Ways the Solar Wind Will Blow You Away
In no uncertain terms, the atmosphere of Venus is doomed. With charged solar wind particles grinding away at its atmosphere and no internally generated magnetic field to protect it, Venus is steadily losing billions of particles of its atmosphere into space every second.
Mars has no internally generated magnetic field either, and most of its atmosphere has already been lost to space. With so little atmosphere left to keep it warm, Mars is a cold, dry little planet.